For the shifting of a transmission, especially where vehicles are concerned, a shifting device is provided in the transmission with the aid of which the individual gear stages can be engaged. As this is done, it is possible that parts of the shifting device can be moved manually by the vehicle driver or, alternating, this function may be carried out by actuators which are energized by at least one auxiliary power medium to execute the necessary movements required by the shifting mechanism.
Customarily, the expended forces which are sufficient for the selection of the individual gear stages are less than those forces to be exerted upon the shifting of the selected gear stage, which has a result that the elements of the selection apparatus on the shifting device can be otherwise dimensioned than are those of the necessary components, which are intended for the execution of the shifting.
The costs for a shifting device of this kind for a transmission are essentially dependent upon the complexity of the employed installed components, upon the materials thereof, upon the required expense for the mechanical working of the components and further upon manufacturing costs for the machining, shaping and heat treatment.
DE A1 198 43 584 makes known a shifting apparatus for a multistage shifting transmission wherein, on a single shifting shaft, a multiplicity of shifting forks are placed. A selection mechanism enables the choice of one of the shifting forks by way of the turning of a shifting shaft. Alternately, if the shifting shaft is axially displaced, then the respectively selected shifting fork is activated to carry out the intended shifting action. A blocking shaft, placed parallel to the shifting shaft, is likewise rotated upon the turning of the shifting shaft and thereby, employing, in its function as a blocking shaft, the movement of such shifting forks which were not chosen as indicated above. The components for this construction must be manufactured in a complex manner and at high cost. Following the assembly of the components, the co-action of the functioning parts generates noise and frequently leads to critical noise problems.
EP-B1 0 633 412 teaches of an actuator for a sliding collar enclosed in a shifting transmission, having a shifting rod located and slidable in the direction of its longitudinal axis on which a shifting fork, as well as a ring-shaped engagement unit, are rigidly affixed. The actuation apparatus is constructed as a combined plastic-metal component, where a metal part, which serves as the ring-shaped engagement unit as well as a core for the shifting rod, is sprayed with a plastic material and the shifting fork consists exclusively of plastic. In this assembly, simply a combination of plastic and metal must be created as a component, in order to assure the required stability of a component necessary for the shifting of a gear stage.
The purpose of the invention is to demonstrate a shifting device, which can be economically manufactured and can operate at a low noise level without containing a complex binding construction.